A collision involving a tractor-trailer closed the southbound Lafontaine Tunnel on Tuesday afternoon.
The large truck crashed and blocked two lanes around 1 p.m., but cleaning up the wreckage took quite a while.
Around 2 p.m. Transport Quebec had to close all lanes heading off the island; this created a monstrous traffic jam, the effects of which were expected to be felt throughout the afternoon rush hour.
One lane was reopened about 3 p.m., but the delays continued, with bumper-to-bumper traffic backing up to Highway 40 -- and creating long delays on westbound Notre Dame Blvd. as drivers slowly made their way to the Jacques Cartier Bridge.
All southbound lanes reopened at 4:20 p.m.
For the latest traffic, check out the map at http://montreal.ctvnews.ca/traffic